#define _CRT_SECURE_NO_WARNINGS 1
#include<bits/stdc++.h>
using namespace std;
int a, b, c;
int main()
{
    cin >> a >> b >> c;
    if (b - c > 0)
        cout << a / (b - c) << endl;
    else
        cout << -1 << endl;
    return 0;
}